Process and apparatus for producing titanium metal continuously



PROCESS AND APPARATUS FOR PRODUCING TITANIUM METAL CONTINUOUSLY FiledMarch '8, 1954 2 Sheets-Sheet 1 INVENTOR Norman Morosh FIGJ AGENT N.MoRAsH PROCESS AND APPARATUS FOR PRODUCING TITANIUM METAL CONTINUOUSLYFiled March 8, 1954- March 11, 1958 2 Sheets-Sheet 2 INVENTOR NormanMorush BY 7 dv lfl m AGENT PROCESS AND APPARATUS FOR mam-Jase TITANIUMMETAL CONTINUOUSLY States Patent F Norman Morash, Westfield, N; 1].,assignor to National Lead Company, New York, N. Y., a corporation ofThis invention relates in general to a method for producing a refractorymetal from a refractory metal halide and specifically to a process andmeans for producing a titanium metal compact of continuous length byreacting titanium tetrachloride with molten alkali metals or alkalineearth metals including magnesium, the instant inyention being animprovement over the process and apparatus disclosed and claimed in the'copending application of Schmidt et al., Serial No. 349,222, filedApril 1:6, 1953, for Continuous Process for Production of Titanium Metalwhich has been assigned to the assignee of the instant application.

As pointed out in said copending application, the processes which haveheretofore been developed for producing titanium metal by reduction oftitanium tetrachloride with alkali metals and alkaline earth metalsincluding magnesium have been, for themost part, batchtyp'e operations.For example, the Kroll Patent No. 2,205,854, June 25, 19 40, and theSchle'chtenet al. Patent No. 2,482,127, September 20, 1949, describemethods for producing titanium metal by reacting titanium tetrachloridewith a molten alkaline earth metal in a reaction pot whereby a titaniummetal product is formed which c'omprises a hard metallic sponge-lLcemass of material. It is characteristic of these processes that themetallic sponge adheres tightly to the walls of thereaction pot and canbe removed therefrom only at great expense, lossjoftime and impairmentof the quality of the titanium metal. Other examples of current effortsto produce titanium metal are the Maddex Patent No. 2,564,337, August14, 1951, and the Winter, In, Patent No. 2,586,134, February 19, 1952,each of whichis directed towards the production' of refractory metals ina manner to avoid the distinct disadvantages of a batch type process,

The copending application of Schmidtet al.,de scribes and claims aprocess andapparatus for producing refractory metal billets ofcontinuouslength While utilizing a reciprocating ram which periodically collectsandcom presses the refractory metal in the reaction vessel toform'successive compacts which, in turn, are integrated and expelledfrom the reaction vessel as a billet of continuous length.

, An object of the instant invention isto. provide an proved method andmeans for producing a, high qi'ia ty refractory metal compactsubstantially cont'i nously Another object of the invention is toprovide an proved method for consolidating and reeoverin g titaniummetal from a molten salt bath as a, titaniutn metal compact ofsubstantially continuous length. v,

A still further object of the mention is to provide improved means forcontinuously forming andexpelling a titanium metal billet from themolten salt bath of a reactor of the type herein described. i p

These and other objects of the instantinventlion will become moreapparent from the following' more 'com plete description and theaccompanying drawings in whichy Figure 1 is a schematic front elevation,partly in sec- 6 2,826,492 Pi'atente d Mar. 11, 1958 7 2 tion, ofapparatus of this invention for producing a titanium metal campactsubstantially continuously.

Figure 2 is anenlarg'ed fragmentary view of the reaction chamber'sh'ownin Figure 1 including details of the compact expelling screws; and

Figure 3 is a transverse sectional view of the apparatus on line 33 ofFigure 2. e In its broadest aspects, the present invention relates to animproved process for forming a refractory metal continuously by reactinga halide of the refractory metal with a molten metallic reducing agentin a molten salt bath to form a refractory metal in the molten saltbath; and continuously consolidating the refractory metal as it isformed in the bath while simultaneously, expelling it therefrom as arefractory metal compact of continuous length.

More specifically, in accordance with the instant inventhan, thesubstantially continuous production of a refractory metal, such as, forexample, titanium metal, is effected by providing a molten salt bath ina reaction chamber having an open bottom end, charging the molten saltbath with a reducing agent such as sodium or magnes'ium metal, andintroducing titanium tetrachloride to form titanium metal dispersedthroughout the molten salt bath; and continuously consolidating thetitanium metal inth'e bath to form a titanium metal compact thereinwhich is simultaneously expelled from the bath and from the bottom endof the vessel'as a single integrated titanium metal compact ofcontinuous length, sometimes referred to hereinafter as a titanium metalbillet.

In one specific embodiment of the invention involving thepreparation ofsubstantially pure titanium metal, a molten salt bath comprising amolten metal halide, preferably magnesium chloride, is provided within asuitable reaction vessel which, as shown schematically in Figure l, isan open ended metallicreaction vessel 8 formed of stainless steel orother suitable type of metal and having, in cross section, theconfiguration of two intersecting circles. The inside dimensions of thevessel may be uniform throughout its length, but superior results have'been achieved by forming its lower end, sometimes hereinafter referredto as the tail-pipe portion 9 thereof, as shown in Figure. l, withprogressively larger internal dimensions so that the metal billet mayfree itself from the walls of the vessel as the billet is expelledtherefrom.

The inside of the reaction vessel above the tail-pipeporti'on 9 thereofconstitutes a reaction chamber 10, the bottom end of which is open butprovided with removable clo-sure means 11 which is preferably in theform of a metal endplug designed to conform in cross section to thecross section of the reaction vessel 8 so as to fit up into the openbottom end thereof; and adapted to be displaceably held therein bysuitable counterbalancing means such as indicated schematically at 12 inFigure l. of the drawings. The counterbalancing means 12 is adapted topermit constant downward displacement of the end-plug 11 duringexpulsionof thecompact and, as hereinafter described, simultaneously toexert sufficient force upwardly against the refractory metal compactsuch that the particles of refractory metal in the bath will beeffectively compacted by the action of the screws and the entrainedsalts pressed out of the compact. A hydraulic piston operating under asteadily decreasing volume of air may be used, but for simplicity ofillustration, a fulcrumed lever of the first class is shown wherein theweight W represents a constant force acting to displaceably support theend-plug 11 in the open bottom end of the reaction chamber.

The salt bath 13 is composed of a halide salt of a metal or metalsselected from the group consisting of the alkali metals alkaline earthmetal including magnesium. It will be found convenient, wheneverpractical, to employ a product of the reduction as the salt bath, forinstance when titanium tetrachloride is being reduced with magnesium,the salt bath may be composed of magnesium chloride. The salt bathmaterials may be introduced into the reaction chamber before the cover14 is put in positron, or may be charged into the chamber by way of afeed pipe, hereinafter described; and'are maintained in a moltencondition therein by heat exchange means which, as shown especially wellin Figure 1, may comprise a furnace arranged around and extendinglongitudinally of the reaction vessel and embodying a plurality ofheating units of varying capacity to provide the heat necessary tomaintain the molten salt bath within a preferred temperature rangehereinafter described.

As shown especially well in Figure l, the lower end of the furnace 15terminates at approximately the bottom end of the reaction chamber 10such that the tail-pipe portion 9 of the reaction vessel is unheated,its overall length being such that the retention time of the compactedmetal billet in the relatively cool tail-pipe portion of the reactionvessel will correspond substantially to the time required for the metalbillet to cool down sufliciently both to freeze the salts entrained inthe billet and to preclude contamination of the billet by the oxygen inthe atmosphere. In this connection auxiliary cooling means, such as, forexample, cooling coils 16, are arranged around the reaction vesseladjacent the upper end of the tail-pipe portion 9, which corresponds tothe bottom end of the reaction chamber 10, to accelerate the dissipationof heat therefrom, if necessary, and hence provide positive control ofthe temperature in this critical region of the reaction vessel.

As indicated by the size and arrangement of the heating units of thefurnace 15, the latter is designed in a manner to heat the reactionchamber, and hence the salt bath 13 non-uniformly, i. e. such that thetemperature of the salt oath adjacent the lower end of the reactionchamber 10 is maintained at a minimum value corresponding substantiallyto the freezing temperature of the salt bath; and increasessubstantially uniformly upwardly to a maximum temperature in the upperregions of the bath for most etficient reaction between the halide ofthe refractory metal and the reducing metal. This temperature range willvary, of course, depending upon the melting points of the materials usedto form the salt bath. In particular, when magnesium chloride isemployed as the salt bath, the temperature gradient of the bath variesfrom the freezing temperature of the salt bath of about 712 C. adjacentthe bottom end of the reaction chamber 10 to a maximum temperature offrom about 880890 C. adjacent the top of the bath, the preferred averagetemperature of the salt bath in the reaction chamber being about 800 C.As pointedout above, the lowest temperature of the salt bath issubstantially adjacent the bottom end of the chamber 10, correspondingto the lower end of the furnace 15 so that at and below this point themolten salt bath will freeze and automatically form an effective sealbetween the compact being formed in the open bottom end of the reactionchamber and the inner walls thereof.

Roughly then, the bottom end of the reaction chamber 10 correspondssubstantially to the freezing level of the,

salt bath within the reaction vessel. Since collection and compacting ofthe titanium metal is carried out in the molten salt bath, the freezinglevel of the molten salt bath represents the very lowest point in thereaction chamber at which the titanium metal compact may be formed.Preferably, however, the end-plug 11 which serves tem- The reducingagent such as magnesium, calcium, sodium or other metal having areducing potential greater than titanium may be charged into the moltensalt bath from the top thereof either in the form of solid metal or in amolten condition.

Since the boiling points'of magnesium and calcium respectively arehigher than the melting point of magnesium chloride, these reducingmetals may be used successfully with a magnesium chloride salt bath.However, since the boiling point of sodium is lower than the meltingpoint of magnesium chloride, it would be necessary, when using sodium asa reducing metal, to employ a salt bath comprising sodium chloride or asuitable eutectic having a melting'point lower than the boiling point ofsodium. When magnesium metal is used as the reducing metal, it ischarged into the reaction vessel in the form of solid rods or bars byway of a feed pipe 17, one end of which intersects the wall of thereaction vessel and the opposite end of which is provided with a pair ofair locks, indicated generally at 18, whereby the rods of magnesiummetal may be introduced successively into the feed pipe while excludingair from entering the reaction chamber. In the preferred constructionshown, the longitudinal axis of the feed pipe 17 extends upwardly at anangle to the longitudinal axis of the reaction vessel, the inner end ofthe feed pipe intersecting the wall of the reaction vessel at a pointabove the top surface 19 of the molten salt bath 13.

The halide of the refractory metal, in this instance vaporous titaniumtetrachloride, may be introduced in either of two ways, i. e. eitherabove the upper surface of the molten salt bath or below the uppersurface of the bath. Preferably, the titanium tetrachloride is fed intothe molten salt bath 13 below the upper surface 19 thereof, by a feedpipe 20, which intersects the wall of the reaction vessel at a pointwell below the upper region of the salt bath, the longitudinal axis ofthe feed pipe 20 extending upwardly at an acute angle with thelongitudinal axis of the reaction vessel. Although the feed pipe 20 isshown, for simplicity, substantially in the plane of the feed pipe 17,it will be understood that the two pipes may be in different verticalplanes.

' As pointed out above, the titanium tetrachloride is fed into the bathpreferably at a point below the upper surface thereof and although thetitanium tetrachloride may be in liquid form, it is preferred to usegaseous titanium tetrachloride. To'this end suitable heating means,indicated generally at 21, may be provided for vaporizing a source 22 ofliquid titanium tetrachloride which is conporarily as the bottomend-closure of the reaction chamber and against which the formation of atitanium metal compact is initiated, is, located within the reactionchamber at a point somewhat above the freezing level of the molten saltbath, and highly satisfactory results have been achieved when theend-plug 11 is located at a point in the chamber at which thetemperature of the magnesium chloridesalt bath is from about'715-720" C.

nected by means of a flexible connection 23 to the feed pipe 20.. Thefeed pipe 20 may be wrapped or otherwise covered with suitable heatinsulating material to prevent condensation of the gaseous tetrachloridetherein.

Since the presence of oxygen in the reaction vessel dur ing the reactionis exceedingly detrimental to the quality of titanium metal produced,the titanium tetrachloride feed pipe is carefully sealed against theadmission of oxygen into the reaction vessel. As one expedient to thisend, suitable apparatus, indicated generally at 24, is connected to theouter end of the feed'pipe 20 to maintain helium or a similar inert gasin the feed pipe at all times so that whenever the vaporous titaniumtetrachloride feed is shut off, sufficient helium gas is present in thefeed pipe to preclude the entry of air or oxygen into the molten saltbath. In like manner, the inert atmosphere within the feed pipeprecludes admission of the molten salt bath up into the open inner endthereof. The vertical distance from the inner end of the titaniumtetrachloride feed pipe 20 to the upper surface 19 of. the salt bath 13may vary to some degree, and'successful operation of the reactor hasbeen achieved when the feed pipe enters the bath at r a 'pointnearer thebottom than the top of the bath.

control means comprising a tap pipe 25, the inner end of which, as shownespecially Well in Figure 1, intersects the wall of the reaction chamberat substantially the height selected for the preferred level of themolten salt. The tap pipe 25 slopes downwardly and its outer end isprovided with a removable closure 26 to permit the introduction of aclean-out rod or the equivalent for clearing the tap pipe in the eventit becomes clogged. Intersecting the tap pipe adjacent its outer end isthe upper open end of a substantially vertical delivery pipe 27, theupper end of which is provided with an extension 28 also capped. Thecapped ends of the respective pipes 25 and 28 provide access to theinteriors of the respective pipes for rodding or clearing the latter ofany condensed materials deposited therein, but which, during normaloperation, are capped to exclude the admission of air to the reactionchamber. Specifically, the material which overflows from the molten bath13 comprises, in the main, molten magnesium chloride which is formed byreaction of the reduced chlorides of titanium with the molten magnesiummetal. Hence, as the reaction proceeds the level of the molten magnesiumchloride rises until it overflows into the tap pipe 25 and thence by wayof the delivery pipe 27 into a heated recovery vessel 29. Sincesolidification of the molten magnesium chloride within the aforemenionedpipes would clog the pipes, the latter are designed not only so'thatthey may be readily rodded but are preferably insulated to insure freeflow 'of the molten magnesium chloride therethrough. 7

Since molten magnesium metal has a lower specific gravity than that ofmolten magnesium chloride, one would expect it to float on the surfaceof the latter and be lost through the tap pipe 25. However, it ispostulated and there is some evidence to indicate that particles oftitanium metal attach themselves to the globules of molten magnesiummetal, thereby increasing the specific gravity of the latter such thatthe globules of molten magnesium metal migrate toward the bottom of thebath. Consequently, no significant amount of molten magnesium metal iscarried out of the bath by way of the overflow pipes.

Pursuant to the objects of the invention, the titanium metal which isbeing continuously formed in the bath by reaction of the reducedchlorides of titanium, i e. the dichlorides and trichlorides, with theglobules of molten magnesium metal, is continuously consolidated, thatis to say, brought together into the form of a single compact mass ofmaterial comprising substantially pure titanium metal. V

In brief, the consolidation of the titanium metal is effectedcontinuously by the use of a pair of continuously rotating self-cleaningscrews which are disposed in the reaction chamber 10, and dimensioned,as shown especially well in Figures 2 and 3, to maintain a free runningfit with the walls thereof; and with adjacent flights of the screws inoverlapping relationship. As the pair of screws rotate theyserve tocollect the titanium metal being forme'd in the bath and carry itdownwardly continuously to the bottom thereof; and simultaneously tocompactithe titanium metal against the upper end of the aforementionedremovable end-plug 11 (or previously compactedtitanium metal) at thebottom of the reaction chamber with sufiicient pressure to squeezetherefrom a large proportion of the inclusions of molten magnesium and/or molten salt and form a substantially solid titanium metal compact. Inaddition, the continuously rotating .screws serve to continuously expelthe compacted titanium metal from the bath by way of the open bottom endof the reaction chamber as a titanium metal billet of continuous length.7

Referring to the drawings, the screws, which are indicated generally at30-'30, are arranged with their longitudinal axes'in the vertical planeof the major axis of the reaction chamber (see Figure 3) and in spacedparallel relationship; and with the adjacent flights'3'1 of therespective screws in overlapping relationship, as shown especially wellin Figure 2, by which arrangement the flights of each screw serve toclean off and otherwise preclude the accumulation of titanium metalparticles on the flights of the other screw. The number of flights oneach screw may vary but preferably the flights should extendsubstantially the entire length of that portion of the screw shaft whichprojects into the reaction chamber and in particular into the moltensalt bath therein. It will be appreciated that during the operation ofthe reactor, innumerable discrete particles of titanium metal as well asincipient titanium metal sponge are dispersed throughout the molten saltbath and tend to accumulate on or freeze to the walls of the reactor aswell as any other solid objects extending into the bath. Hence, it isimperativethat the screws be constructed as shown not only so that theperirneters of the flights of the screws will be disposed immediatelyadjacent the inner walls'of the reactionchamber, which to this end isformed to have, in cross section, the shape of two intersecting circles,and so that the flights of the screws will overlap throughout theportions thereof extending into the reaction chamber. While by and largethe greater amount of titanium metal is formed in the molten salt bath,some is formed by reaction of the vapors which ascend into the upper endof thereaction chamber above the upper level of the bath and precipitateout on the upper walls and upper ends of the screws. Hence, thedesirability of providing overlapping flights throughout the lengths ofthe screws. v

The lower ends of the screws are shown terminated at a pointsubstantiallyhalf-way between the inlet of the feed pipe 20 and thebottom end of the reaction chamber, and while this disposition of theterminal ends of the screws is wholly satisfactory, it will beunderstood, that it 'is not critical and that variation thereof may bemade and are contemplated within the scope of the invention.

The portion of the screws which extend upwardly above the upper end wallor cover 14 of the reaction chamber are hereinafter referred was thescrew shafts 32. These screw shafts are rotatably supported in a bearingstructure/Which, as shown especially well in Figure 1, comprises abushing housing 33 mounted on the top of the cover 14 of the reactionchamber; and a cage 34 which extends upwardly from the cover 14 and isprovided with transversem'emb'ers 35 which serve to support a pair ofvertically spaced stabilizing bearings 36-36 and a thrust bearing 37,the lat ter being disposed substantially intermediate the stabilizingbearings. The bushing housing 33 is provided with suitable sealingglands to preclude the entry of air into the reaction chamber while thethrust bearings serve to support the shafts against verticaldisplacement.

The shafts 32 are adapted to be rotated in opposite directions and tothis end are provided with a motor driven gear-train indicated generallyat 38 which as shown is located above the upper stabilizing bearing.Above the gear-train, each shaft is provided with a sealed cap 39rotatably engaged thereon and within which its respective screw shaftterminates, each cap having a pair of radially extending pipes 40 and 41respectively for delivering a coolant into and from the upper end of itsshaft. 7

In this connection it should be explained that since the temperaturesemployed in carrying out the reaction in the reaction chamber are in therange of from 712 C.

to 890 C., it is preferable to cool the screws to prevent theirdistortion. Consequently, the screws are of hollow construction, that isto say both the shafts and flights are provided with passagestherethrough, as shown especially well in Figure 2, whereby a coolantmay be circulated through the shafts and flights to preclude overheating. Hollow flight screws of this general type have i been used inindustry in other capacities, and consequently the structural details ofthe screws do not form a part of theinstant invention but are shown forclarity and as an illustration of one type of hollow flight screw 7which may be used successfully for the continuous production of arefractory metal billet in the manner of this invention. 7 7

As shown, each screw shaft 32 comprises an inner tube 42 and an outertube 43, the coolant being delivered by the inlet pipe 40 into the upperend of the inner tube 42 and passing down to the bottom end of the screwfrom which point the coolant returns upwardly through the hollow flights31 and the annular passage between the inner and outer tubes into thesealing cap 39 at the upper end of the shaft and from thence into theoutlet pipe 41.

Any suitable type of coolant may be used and preferably one which willnot react adversely with the reaction products in the reaction vessel inthe event of a leak or break occurring in one of these screws. Titaniumtetrachloride is suggested as a satisfactory coolant since titaniumtetrachloride is one of the reactants and consequently cannot beexpected to cause any serious damage if inadvertently released into thereaction chamber. By circulating the coolant at a rate such as tomaintain the temperature of the coolant preferably below its boilingpoint, although not necessarily so, the screws may be effectively cooledto preclude deterioration and destruction.

Although the drawings of the apparatus shown are schematic in nature,nevertheless they tend to illustrate the principal elements of a type ofapparatus which may be used to produce titanium metal compacts. However,some modifications of the apparatus are contemplated within the scope ofthe invention, particularly changes whereby the overall height of thereaction chamber may be decreased such that shorter screws may be usedperhaps to better advantage.

As pointed out above, the temperature of the salt bath varies throughoutthe bath and is critical for the successful operation of the reactor.This is particularly true of the temperature of the bath at the lowerend of the reaction chamber where freezing of the salt bath must occurin order to insure a seal between the compact being formed and the openbottom end of the reaction chamber. For a magnesium chloride bath thefreezing point is about 712 C. which is, therefore, the maximumpermissible temperature of the bath at the open bottom end of thereaction chamber. If other salts are employed, then the freezingtemperature of the bath would be different. For example, if a sodiumchloride bath is employed, then the maximum temperature of the bath atthe open bottom end of the reaction chamber would be about 800 C.

The process by which the titanium metal billet is formed using theapparatus of this invention is illustrated especially well in Figure land described briefly as fol lows: The reaction vessel is made ready foroperation by adjusting the counterbalance 1.2. so as to hold the steelend-plug ill in place in the bottom end of the reaction chamber 19 andpreferably at a point at which the temperature of the bath is slightlyabove freezing, as for example about 7l5720 C. If available, it ispreferred to drop a piece of titanium metal sponge into the reactionchamber onto the top of the end-plug 11 to serve as a starting materialon which to form a compact in which instance the end-plug 11 would belocated further down in the chamber so as to bring the titanium metalsponge at the aforesaid temperature level.

The molten salt bath R3 in the reaction chamber is prepared by addingcrushed anhydrous magnesium chloride to the reactor and then heating thereactor to melt the anhydrous magnesium chloride and establish anaverage temperature in the molten salt bath of about 800 C. Heat is alsoapplied to the magnesium chloride recovering vessel 29 to bring it up toa temperature of about 800 C., and similarly heat is applied to thetitanium tetrachloride feed pipe and the magnesium chloride overflowpipes to prevent solidification of the respective compounds therein.

After purging the entire system of oxygen and other deleterious gases,by means of the-helium source 24 which is attached to the feed pipe 20,the valves of the titanium tetrachloride vaporizing chamber 22 areopened to admit vaporous titanium tetrachloride into the feed pipe.

For optimum performance, the titanium tetrachloride vaporizing chambershould be kept at a temperature from between 500600 C. and the feed pipeat a temperature between 300400 C.

The magnesium metal in the form of half-pound sticks is then added intothe reaction chamber 10 from the air lock 18, the vaporous titaniumtetrachloride being concurrently fed into the bath initially at arelatively low rate and subsequently at an increased rate as thereaction proceeds. The magnesium metal is preferably added in amounts of5% excess over the theoretical amount to reduce the titaniumtetrachloride introduced.

As the titanium metal begins to form in the bath, the motor drivenscrews 30-30 are started and turned continuously at a very slow rate ofrotation so as to preclude sufficient agitation of the salt bath aswould unify the temperature of the bath, as for example no faster thanabout 10 R. P. M., whereby the flights 31 of the screws collect and movethe particles of titanium metal being formed in the bath downwardly tothe bottom thereof. A coolant is simultaneously circulated through thescrews in the manner hereinabove described. Molten magnesium chloridewill have formed in the bath, and some of this molten magnesium chloridewill penerate down between the walls of the reaction chamber and theend-plug 11, as indicated in Figure 2, but is effectively prevented fromescaping from the lower open end of the reaction chamber by being frozenat a point substantially opposite the cooling coils 10 of the reactionchamber to form a seal.

As the reaction continues, the amount of titanium metal collected andcompressed at the bottom of the chamber by the action of the screwssteadily increases until a point is reached at which the compressionexerted by the screws on the compacted metal exceeds the forcesupporting the end-plug 11 in the bottom of the reaction chamber. Thisforce may be a combination of that exerted by the fulcrumed weight Wandthe friction force of the frozen magnesium chloride. When thecompression force exerted by the screws exceeds the aforementioned forcewhich supports the end-plug 11 in the bottom of the reaction chamber,the end-plug together with the compacted titanium metal begin to movedownwardly slowly through the tail pipe portion 9 of the reactionchamber, the magnesium chloride seal being constantly maintained by thefreezing of the magnesium chloride as it reaches the bottom end of thereaction chamber substantially opposite the cooling coil 16. The speedof movement of the compact is governed, of course, by the rate at whichthe titanium metal is being collected and compacted by the continuouslyrotating screws. Once the compact has begun to move downwardly, itsmovement is continuous and steady, the force differential between thecompacting force of the screws and the constant combined counteractingforces exerted by the fulcmmmed weight W and the friction force of thefrozen magnesium chloride being sufficient to press substantially all ofthe molten magnesium chloride salts from the compact in the molten saltbath whereby the billet expelled fromthe tail pipe of the reactor is ofremarkably uniform density and composition.

The billet comprises, in the main, substantially pure titanium metal andrelatively minor amounts of'frozen salt which may be separated from thepure titanium metal by well known leaching and/ or distillationtechniques. It

From the foregoing description it will be manifest that the process andapparatus of the present invention provides a continuous, relativelysimple, inexpensive and highly productive method for producing titaniummetal of high purity and ductility; and that the titanium metal billetis extruded as a continuous length of substantially solid metal fromwhich impurities may be readily removed at minimum expense, therebyprecluding the high losses of metal,

time and equipment which have characterized earlier batch methods forproducing refractory metals.

Although the invention has been illustrated by its application to theproduction of titanium metal using magnesium as a reducing metal, it iswithin the purview of the invention to utilize other reducing metals,such as sodium; and to form other refractory metals, such as zirconium,from the halide of the metal by the process and apparatus hereinabovedescribed.

While this invention has been described and illustrated by the examplesshown, it is not intended to be strictly limited thereto, and othervariations and modifications may be employed within the scope of thefollowing claims.

I claim:

1. A process for producing a refractory metal compact which comprises:providing a reaction bath consisting of a molten halide salt of a metalselected from the group consisting of the alkali metals and alkalineearth metals including magnesium; introducing a reducing metal into saidmolten metallic salt bath; feeding a halide of said refractory metal tosaid molten metallic salt bath and reacting said halide with saidreducing metal to form a refractory metal in said bath; and continuouslyconsolidating and compressing the refractory metal in said bath toproduce therein and simultaneously expel therefrom a relatively denserefractory metal compact of continuous length.

2. A process for producing a refractory metal compact which comprises:providing a reaction bath consisting of a molten halide salt of a metalselected from the group consisting of the alkali metals and alkalineearth metals including magnesium; introducing a reducing metal into saidmolten metallic salt bath; feeding a chloride of said refractory metalto said molten metallic salt bath and reacting said chloride with saidreducing metal to form a refractory metal in said bath; continuouslyconsolidating and compressing the refractory metal in said bath toproduce therein and simultaneously expel therefrom a dense refractorymetal compact of continuous length; and maintaining a seal between saidmolten metallic salt bath and a portion of said expelled compact byfreezing a portion of said salt bath.

3. A process for producing a titanium metal compact which comprises:providing a bath consisting of molten magnesium chloride; introducingmagnesium metal into said magnesium chloride bath to form moltenmagnesium metal in said bath and reacting said titanium tetrachloridewith said magnesium metal to form titanium metal in said bath;continuously collecting the titanium metal in said bath and continuouslycompressing the collected titanium metal in said bath with a compressionforce sufiicient to squeeze substantially all inclusions of said moltensalt from said collected titanium metal and form a relatively densetitanium metal compact in said bath, said compression force beingsuflicient also to simultaneously expel said titanium metal compact fromsaid bath.

4. A process for producing a titanium metal compact which comprises:providing a bath consisting of molten magnesium chloride in a reactionchamber; introducing magnesium metal into said magnesium chloride bathto form molten magnesium metal in said bath; heating said bath in amanner to provide a temperature gradient in said bath ranging from thefreezing point of said magnesium chloride adjacent the bottom of saidreaction chamber to a temperature of at least about 840 C. adjacent theupper end thereof; feeding titanium tetrachloride to said magnesiumchloride bath and reacting said titanium tetrachloride with saidmagnesium metal to form titanium metal in said bath; continuouslycollecting and compressing the titanium metal into the bottom of saidreaction chamber at a level above the freezing point of said magnesiumchloride bath to produce therein and simultaneously expel therefrom arelatively dense titanium metal compact.

5. A process for producing titanium metal compact which comprises:providing a bath consisting of molten magnesium chloride in a reactionchamber having a removable end-closure adjacent its bottom end;introducing magnesium metal into said magnesium chloride bath to formmolten magnesium metal in said bath; feeding titanium tetrachloride tosaid magnesium chloride bath and reacting said titanium tetrachloridewith said magnesium metal to form titanium metal in said bath;continuously collecting titanium metal in said bath; continuouslycompressing the collected titanium metal in said bath against saidremovable end-closure with sufficient force to squeeze substantially allinclusions of said molten salt from said collecting titanium metal andform a relatively dense titanium metal compact in said bath, saidcompression force serving simultaneously to provide a pressuredifferential between the compact and the displaceable end-closure in adirection to effect displacement of said removable end-closure, therebyto displace the titanium metal compact continuously from said reactorchamber.

6. A process for producing substantially pure refractory metal whichcomprises: providing a bath consisting of a molten halide salt of ametal selected from the group consisting of the alkali metals andalkaline earth metals including magnesium; introducing a reducing metalinto said molten metallic salt bath to form molten reducing metal insaid bath and reacting a halide of said refractory metal with saidreducing metal to form a refractory metal in said bath; continuouslycollecting and compressing the refractory metal in said bath to producetherein and simultaneously expel therefrom a relatively dense compact ofrefractory metal including entrained salts; and then treating saidcompact to separate the entrained salts from the refractory metal.

7. In a process for producing a refractory metal by reacting amultivalent halide of the refractory metal with a reducing metal in abath consisting of a molten halide salt of a metal selected from thegroup consisting of alkali metals and alkaline earth metals includingmagnesium, the steps comprising: introducing the halide of saidrefractory metal into said bath to react with said reducing metal andform said refractory metal in said bath; and continuously collecting andcompressing the refractory metal in said bath to form a relatively denserefractory metal compact therein and simultaneously to expel therefractory metal compact from said bath.

References Cited in the file of this patent UNITED STATES PATENTS2,171,439 Von Zeppelin Aug. 29, 1939 2,271,960 Taylor Feb. '3, 19422,549,642 Seelig Apr. 17, 1951 2,564,337 Maddex Aug. 14, 1951 2,570,989Seelig Oct. 9, 1951 2,618,550 Hampel et al Nov. 18, 1952 2,676,882 HatchApr. 27, 1954 2,753,254 Rick July 3, 1956 2,758,921 Schmidt Aug. 14,1956 OTHER REFERENCES Hatch et al.: Abandoned application Serial No.189,404, filed Oct. 10, 1950.

1. A PROCESS FOR PRODUCING A REFRACTORY METAL COMPACT WHICH COMPRISES:PROVIDING A REACTION BATH CONSISTING OF A MOLTEN HALIDE SALT OF A METALSELECTED FROM THE GROUP CONSISTING OF THE ALKALI METALS AND ALKALINEEARTH METALS INCLUDING MAGNESIUM, INTRODUCING A REDUCING METAL INTO SAIDMOLTEN METALLIC SALT BATH: FEEDING A HALIDE OF SAID REFRACTORY METAL TOSAID MOLTEN METALLIC SALT BATH AND REACTING SAID HALIDE WITH SAIDREDUCING METAL TO FORM A REFRACTORY METAL IN SAID BATH, AND CONTINUOUSLYCONSOLIDATING AND COMPRESSING THE REFRACTORY METAL IN SAID BATH TOPRODUCE THEREIN AND SIMULTANEOUSLY EXPEL THEREFROM A RELATIVELY DENSEREFRACTORY METAL COMPACT OF CONTINUOUS LENGTH.